ILC-BAW1 Summary and Recommendations Akira Yamamoto, Marc Ross and Nick Walker GDE Project Managers Reported at BAW1, held at KEK, Sept. 10, , A. YamamotoBAW1 Summary1

, A. YamamotoBAW1 Summary 2 SB2009 Themes N Walker

Global Plan for SCRF R&D Year Phase TDP-1TDP-2 Cavity Gradient in v. test to reach 35 MV/m  Process Yield 50%  Production Yield 90% Cavity-string to reach 31.5 MV/m, with one- cryomodule Global effort for string assembly and test (DESY, FNAL, INFN, KEK) System Test with beam acceleration FLASH (DESY), NML (FNAL) STF2 (KEK, extend beyond 2012 ) Preparation for Industrialization Production Technology R&D , A. Yamamoto3BAW1 Summary

, A. Yamamoto BAW1 Summary 4 Baseline Assessment WorkShops WhenWhereWhat WAB 1Sept. 7-10, 2010 KEK1.Accelerating Gradient 2.Single Tunnel (HLRF) WAB 2Jan 18-21, 2011 SLAC3.Reduced RF power 4.e+ source location Baseline Assessment Workshops Face to face meetings Open to all stakeholders Plenary

BAW1 Objectives and Goals Assess technical proposal in SB2009 Confirm R&D Plan required and Goal in TDP-2 Discuss Impact across system interfaces, cost, and schedule, Discuss toward consensus in GDE and Physics/Detector groups to prepare for TLCC , A. YamamotoBAW1 Summary5

Subjects discussed in Sessions DateMain ThemeTasks Sept. 7Introduction HLRF-KCS: Design and R&D RDR: Technical Make the workshop tasks clear Process for the reality including cost Feasibility as a backup solution Sept. 8DRFS: Design and R&D LLRF/Control Discussions Process for the reality including cost R&F operation margin for cavity/accelerator Recommendation Sept. 9Cavity Gradient: R&D Discussions Strategy for cavity gradient improvement Short-term and long-term strategy to be clear Sept. 10ML Accelerator Gradient Discussions Accelerator gradient including spread, Appropriate balance of gradient in cavity/cryomodule/accelerator, and Adequate margin in accelerator operation Recommendation , A. YamamotoBAW1 Summary6

Time-Table / Agenda (Sept. 7) updated: August 27 DayAm/pmSubjectChair/presenter 9/7Single Tunnel ML Design and HLRF -1 S. Fukuda / C. Nantista 9: min Opening and Introduction - Opening address - Report from AAP - BAW1 objectives and goals Chair: S. Yamaguchi - A. Suzuki (KEK-DG) - E. Elsen - A. Yamamoto (GDE-PM) 10:45 90 min Single tunnel CF design and HLRF design - Single tunnel CF design status (1 hour) - General HLRF design in SB2009 (30 min) Chair: T. Shidara - A. Enomoto - S. Fukuda 13: min HLRF KCS -KCS design and R&D status (45 min) -Demonstration of feasibility (45 min) Chair: S. Fukuda - C. Nantista - C. Adolphsen 15: min HLRF – EU XFEL and RDR - Introduction (20 min) - Experience from XFEL (1 hour) - RDR configuration (as backup) (10 min) - Discussion (15 min) Chair: N. Walker -M. Ross -W. Bialowons - S. Fukuda - ALL , A. YamamotoBAW1 Summary7

Time-Table / Agenda (Sept. 8) DayAm/pmSubjectConvener/presenter 9/8Single Tunnel ML Design and HLRF -2 S. Fukuda / C. Nantista 9:00DRFS -DRFS design and R&D status -Installation strategy -(1 hour total) Chair: C. Nantista - S. Fukuda 10:45HLRF and LLRF -LLRF requirements/issues for KCS 30 -LLRF requirements/issues for DRFS 30 -Requirements from Beam Dynamics 30 Chair: T. Shidara - C. Adolphsen - S. Michizono - K. Kubo 13:30Operational consideration - Sorting cavities in relation with HLRF 30 - Gradient and RF Power Overhead 30 Chair: C. Adolphsen - S. Noguchi - J. Cawardine 15:45Discussions and Recommendations - General discussions and questions - Summary and recommendations Chair: A. Yamamoto - TBD - ALL , A. YamamotoBAW1 Summary8

Single Tunnel Proposal: intro 1 The proposal to go to a single tunnel solution for the Main Linac technical systems remains essential that outlined in the SB2009 report. The primary motivation was and remains a reduction in project cost due to the removal of the service tunnel for the Main Linac. The original proposal was based on the adoption of two novel schemes for the HLRF: – KCS – DRFS KCS has been identified as a preferred solutions for ‘flat land’ sites where surface access (buildings) is not restricted DRFS has been identified as being preferred solutions for mountainous region where surface access (buildings) is severely limited. Having both R&D programmes in parallel can be considered as risk-mitigation against one or other of them failiing. It is acknowledged that both these schemes require R&D – Programmes are detailed in the R&D Plan Release 5 At the time of submission in December 2009, the two primary obstacles to adoption of a single tunnel were identified as – Safety egress – Operations & Availability , A. Yamamoto9BAW1 Summary

Resonant Line 5.0 MW 350 MW 80 m of WC1890 back-shorted tap-in Resonant Ring 5.0 MW 350 MW 160 m of WC1890 directional coupler In FY11: Also extend pipe system to 80 m and add bend prototype tap-off tap-in phase shifter In FY12: Use resonant ring to test ‘final design’ bends and tap-in/off

11 BAW1.DRFS (S. Fukuda) 8/09/2010 Task and R & D schedule of DRFS in KEK R&D study is easy since the DRFS system is not large. Task force team of DRFS starts and try to solve the problems of DRFS. Prototype RF unit is manufactured in FY09 Further R&D required for the DRFS RF system is continued from FY09. Three year R&D budget was approved. Permanent magnet, high voltage SW and IGBT will be studied intensively. Prototype will be evaluated in the S1 global test (2 Klystron DRFS) And then installed in the buncher section of STF-II aiming for the realistic operation. More large scale of DRFS (4~5 Klystron DRFS) is planed for STF-II in KEK. l S1-Global Plan

Single Tunnel Proposal: intro 2 Both these issues were addressed during the 2009 and the successful results reported in the SB2009 proposal. – The conclusions of these studies were later accepted by both AAP and PAC The remaining identified issues were with the technical feasibility and cost of the HLRF solutions upon which the single- tunnel proposal was based. Two components to successful adoption were identified – Definition of acceptance criteria for TD Phase R&D for successful demonstration of one or more of the novel proposed schemes – Inclusion in the designs of a risk-mitigation strategy, whereby a fall-back to the RDR HLRF Technical Solution (in a single-tunnel) could be adopted, should the associated R&D not be considered successful. The remainder of these slides deals with these two additional points , A. Yamamoto12BAW1 Summary

RDR HLRF Tech. Solution 1 Two scenarios have been cursorily studied for support of an RDR-like HLRF solution in a single-tunnel 1.10MW MBK + (Marx) Modulator in the tunnel 2.XFEL-like solution with modulators (low-voltage) accessible in cryo refrigeration builds/caverns, with long pulsed cables feeding 10MW MBKs (via a pulse transformer) in the tunnel. Both are considered technically feasible. For 1, early investigations show the tunnel diameter would need to increase to 6.5m – This represents an estimated 10% increase in cost/unit tunnel length (~0.5% TPC) considered acceptable. – Current availability* simulations (cf SB2009 proposal) suggest an additional ~5% linac overhead (~2.5% TPC) For 2: – additional space for modulators in halls/caverns is required. – Cost of 3000 km of pulsed cable will be required. – Re-design of tunnel cross-section needed to accommodate cables. – Current availability* simulations (cf SB2009 proposal) suggest an additional ~2.5% linac overhead (~1.3% TPC) * see later comments on availability , A. Yamamoto13BAW1 Summary

BAW1 RDR Confg For Mntn Rgn (S. Fukuda)14 3D of RDR single tunnel plan ( Bouncer Modulator)- (1) Cross Sectional View Cryomodule is installed on the floor to avoid the vibration problem which possibly affects to the beam instability. RF Power distribution system are under the passage in the middle of the tunnel. 6.5m

RDR HLRF Tech. Solution 2 It is proposed that these RDR-like single-tunnel solutions be carried forward in parallel, to enough detail to support a cost estimate (incremental) This estimate – together with the scope of the necessary re-design work to adopt one of the scenarios, will be factored into the TDR Risk Assessment The main R&D and AD&I effort will continue to pursue the preferred baseline solutions for KCS and DRFS. In order to reduce the number of scenarios to be developed, we propose to phase out one of these RDR-like options within the next six-months * see later comments on availability , A. Yamamoto15BAW1 Summary

Time-Table / Agenda (Sept. 9) Day Am/pm SubjectConvener/presenter 9/9Cavity: Gradient R&D and ML Cavity Gradient R. Geng/A. Yamamoto 9:00Introduction and Current Status - Technical address for the 2 nd part of WS - Overview from RDR to R&D Plan 5 - Progress of cavity gradient data-base/yield Chair: M. Ross - A. Yamamoto - R. Geng - C. Ginsburg 10:45 R&D Status and further R&D specification - Fabrication, testing, & acceptance for XFEL/HG - R&D expected in cooperation w/ vendors - R&D w/ a pilot plant w/ vendor participation Chair: K. Yokoya - E. Elsen - M. Champion - H. Hayano 13:30Short-tem R&D and Specification - Field emission and R&D strategy - Gradient, Spread, Q0, Radiation: R&D specification, standardization Chair: C. Pagani - H. Hayano - R. Geng 15:45Long-term R&D ACD subjects and goals - Seamless/hydro-forming, Large Grain, Cavity shape variation, VEP, Thin Film, - Further R&D toward TEV/ML - Discussions for Cavity R&D and Recommendations Chair: A. Yamamoto - R. Rongli to lead discussions , A. YamamotoBAW1 Summary16

Time-Table / Agenda (Sept. 10) DayAm/pmSubjectConvener/presenter 9/10 ILC accelerator gradient and operational margin A. Yamamoto and J. Kerby 9:00 Gradients from VTS to Operation - Introduction: Overview on ILC gradient specification at each testing / operation step - Terminology definition - Operational results from VT/HTS/CM tests in data base - Operational results from STF VT/CM tests at KEK Chair: H. Hayano - A. Yamamoto - M. Ross - C. Ginsburg - E. Kako 10:30 Operational margin - Lorentz Force Detuning and Effects on op. margin - Comments from LLRF and Beam Dynamics - Comments onAcceerator Operation gradient margin Chair: N. Toge - E. Kako - (K. Kubo/C. Michizono) - N. Walker 13:30 Cost Impacts - Reminder on cost effects - List of systems / technical components affected by gradient specification change - A plan to prepare for communication w/ industries Chair: N. Walker - P. Garbincius - J. Kerby - A. Yamamoto 15:15 General Discussion and recommendation - General discussions - Summary and recommendations Chair: A. Yamamoto - All 17:00 - End , A. YamamotoBAW1 Summary17

Cavity Gradient Progress ILC-GDE Cavity Database Team Progress report – C. Ginsburg et al. – as of June 30, , A. YamamotoBAW1 Summary18

Gradient Spread and Standard Deviation , A. YamamotoBAW1 Summary19 As of June 30, 2010 Average: ~ 36 MV/m at gradient cut at 25 MV/m Standard deviation: ~ 5 MV/m gradient cut at 25 MV/m

Gradient Improvement Plan Based on Recent Understanding due to Globally Coordinated S0 Program Highest priority is to push yield up near 20 MV/m – the yield drop due to local (geometrical) defects near equator weld. – Fab. QA/QC – Mechanical polish prior to heavy EP – Post-VT local targeted repair – Seamless cavity – Large-grain mat. From ingot slicing – Fine grain mat. Optimization Also high priority is to suppress field emission at high gradient (up to 42 MV/m) – and quantify its effect on cryogenic loss and dark current. Eliminate Local defect (geo.) near equator weld Remove local defect (comp.) and field emitter , A. Yamamoto20BAW1 Summary

, A. YamamotoBAW1 Summary21 Basic R&D Efforts in TDP-2

From R. Geng , A. YamamotoBAW1 Summary22

R. Geng , A. YamamotoBAW1 Summary23

ILC ML Cavity Gradient R&D Milestones and ML operational Specification , A. YamamotoBAW1 Summary24

R&D Milestone Technical R&D Plan (revised: Rel-5) StageSubjectsMilestones to be achieved Year S09-cell cavity 35 MV/m, max., at Q0 ≥ 8E9, with a production yield of 50% in TDP1, and 90% in TDP2 1), 2) 2010/ 2012 S1Cavity-string 31.5 MV/m, in average, at Q0 ≥ 1E10, in one cryomodule, including a global effort 2010 S2 Cryomodule- string 31.5 MV/m, in average, with full-beam loading and acceleration , A. YamamotoBAW1 Summary25

ILC Accelerator, Operational Gradient Strategy for Average Accelerating Gradient in the ILC operation: – Overview and scope of 'production yield' progress and expectations for TDP, including acceptable spread of the gradient needed to achieve the specified average gradient, – Cavity Gradient, Q0, and Emitted Radiation in vertical test, including the spread and yield, – Cryomodule Gradient, Cryogenic-load and Radiation, including the gradient spread and operational margin with nominal controls, – ILC Accelerator Gradient, Cryogenic-load and Radiation, including the gradient spread and the operational margin with nominal controls – Strategy for tuning and control, including feedback, control of ‘Lorentz force detuning’, tolerances and availability margin, – Impact on other accelerator systems: CFS, HLRF, LLRF, Cryogenics, and overall costs , A. Yamamoto26BAW1 Summary

A possible balance in ILC ML Accelerator Cavity Specification , A. YamamotoBAW1 Summary27 Single 9-cell cavity gradient String Cavity gradient in cryomodule w/o beam String cryomodule gradient in accelerator with beam 35 MV/m, on average w/ spread above a threshold 34 MV/m, on average (or to be further optimized) 31.5 MV/m, on average (or to be further optimized)

Summary HLRF/LLRF design with Single Tunnel layout ML Accelerator Gradient , A. YamamotoBAW1 Summary28

HLRF/LLRF Design with Single Tunnel The main proposal is to go to a single tunnel solution for the Main Linac technical systems remains essential that outlined in the SB2009 report, and is based on the adoption of two novel schemes, requiring RD, for the HLRF in the single tunnel: – KCS: preferred solutions for ‘flat land’ sites – DRFS: preferred solutions for mountainous region Two backup scenarios are proposed for supporting RDR-like HLRF solutions in a single-tunnel 1.10MW MBK + (Marx) Modulator in the tunnel 2.XFEL-like solution with modulators (low-voltage) accessible in cryo refrigeration builds/caverns, with long pulsed cables feeding 10MW MBKs, via a pulse transformer, in the tunnel. Both are considered technically feasible, and no R&D program is proposed. We propose to phase out one of these RDR-like options within the next six- months, in order to reduce the number of scenarios to be developed. There are comments on the Original RDR HLRF solution with two tunnel to be a fall- back solution, although PM proposal to seek for the RDR-likeHLRF solution in the single tunnel to keep effective design work , A. YamamotoBAW1 Summary29

ILC-ML SCRF Cavity Gradient Specifications proposed, based on R&D Effort and Milestone/Goals Cost-relevant design parameter(s) for TDR ML cavity gradient Specification R&D Milestone Relevant R&D Programme Mass production distribution (models) S0 9-cell Cavity Gradient in vertical test 35 MV/m, average - Spread: 28 – 42 MV/m (+/- 20 % or less) 35 MV/m at 90 % yield including 2 nd pass, (eq. > 38 MV/m, average ) S0 Cryomodule Operational Gradient 34 MV/m, average CM Obs. G. Limit = 3 % + ** S1 ML Operational Gradient 31.5 MV/m avg - Spread: 25 – 38 MV/m (+/- 20 % or less: TBD) 31.5 MV/m, average Op. G lim = 1.5 MV/m** Cntrl margin = 3 %** S2 (S1*) Required RF power overhead for control 10% (TBD)S2 (S1*) , A. YamamotoBAW1 Summary30 ** as milestone for R&D

Accelerator Gradient Common understanding and Recommendation Observation – Challenging operational margin in accelerator operation to be reliable enough for sufficient availability for physics run. Our Strategy Proposed – Provide two major guidelines R&D milestone: 35 MV/m with 90 % yield (eq. > 38 MV/m on average), including 2 nd pass, ILC ML Cavity specification: 35 MV/m on average with spread, – Make our best effort with forward looking position to realize the accelerator operational gradient to be 31.5 MV/m, on average with reasonable gradient spread (< ~ +/-20 %). We require an additional HLRF power of 10 %. – Keep cost containment concept, and prepare for the industrialization including cost and quality control. – Ask physics/detector groups to share our observation and forward looking strategy , A. YamamotoBAW1 Summary 31

Acknowledgment on behalf of ILC-GDE Project Managers Many thanks for all participants at KEK and through webex. We would thank the LOC led by Seiya Yamaguchi and organized by Tetsuo Shidara, Tomiko Shirakata, Kazuko Toyomura, Nobuko Kobayashi, Kazuko Nagai, Emiko Kotaki, H. Hayano, Takayuki Saeki, and Araki Sake, for their much effort to bring the BAW1 successfully carried out , A. YamamotoBAW1 Summary32

backup , A. YamamotoBAW1 Summary33

BAW1 Summary 34 Higher Gradient Operation with Better Electric Power Efficiency Small Tuning Range & Less DLD Effect Cavity Grouping with Over-Coupling , A. Yamamoto

BAW1 Summary 35 How should we do for Degraded Cavity ? To Save other Good Cavities, We should have Tunability for RF Power & Coupling , A. Yamamoto

BAW1 Summary 36 Quench Gradient Feed-back Limit ( LLRF ) V-Sum Feed-back Margin Time Gradient Highest Gradient Operation 1 ~ 2 MV Lorentz Detuning Compensation Error Q L = 3x10 6, Δf = 50 Hz, ψ = 13° ーー  ΔV = - 5 % QL = 2.0x10 6, Δf = 50 Hz, ψ = 8.7°  ΔV = % Operating Gradient , A. Yamamoto

Ideally, all cavities reach their respective quench limits at the same forward power 25.7 MV/m 28.5 MV/m 4.6 MW klystron power (est.) 5.5 MW klystron power (est.) 23.0 MV/m 26.1 MV/m ACC6 C2 will quench first (artifact of RF distribution forward power ratios) Reality: errors in power ratios due to manufacturing tolerances of rf attenuators (In this case: tolerances are of the order +/-0.1dB) Avg Emax: 31.4 MV/m Avg Emax: 28.6 MV/m Avg Emax: 27.9 MV/m Avg Emax: 23 MV/m 37BAW1 Summary , A. Yamamoto

Summary from S. Michizono 38 BAW1 Summary (1)LLRF overhead ~5% (2)Cavity gradient tilt (repetitive) ~5% (3)Pulse-to-pulse gradient fluctuation ~1%rms RDRDRFS (PkQl)DRFS(Cavity grouping) Operation gradientMax. 33 MV/mAverage 31.5 MV/mMax. 38 MV/m RF source10 MW800 kW Waveguide loss8% power2% power Static loss (Ql, Pk)2% power Kly Hv ripple2.5% power Microphonics2% power Reflection0% power14% power0% power Other LLRF margin10% power 5%~10% power Ql tolerance3% (2) Pk tolerance0.2dB (2) Detuning tolerance15Hz rms(3)20Hz rms (3) Beam current offset2% rms (3) We have to examine these numbers experimentally. Tolerance should be discussed with cavity and HLRF group. If the tolerance is smaller, better gradient tilt would be possible , A. Yamamoto

Gradient and Spread as of June, , A. YamamotoBAW1 Summary39

BAW1 Summary 40 Quench Gradient Feed-back Limit Feed-back Time Gradient Highest Gradient Operation From S. Nogichi Operating Gradient One Cavity – One Klystron Best Configuration Beam Timing , A. Yamamoto

Subjects to be further studied in TDP-2 Further Studied in TDP-2 – How wide cavity gradient spread may be acceptable in balance of HLRF power source capacity and efficiency? – How large operational margin required and adequate in cryomodule and accelerator operation? , A. YamamotoBAW1 Summary41